Well seismic tie issue

[Arnab Kumar Pal]

Sir,

We are able to perform well seismic tie but the correlation coefficient r is coming out to be very low even after phase rotation and wavelet tapering of the initial wavelet. Kindly guide me on improving the r value. 

Thank you

Arnab 

[Paul de Groot]

Dear Arnab,

You can try to improve the tie by stretching and squeezing the synthetic. This can be done in an iterative manner. You start with a synthetic wavelet or a stochastic wavelet. Next, you force some events on the synthetic to match corresponding events on the measured seismic. This results in a deterministic wavelet that can be used in the next phase of matching events. This step can be repeated a few times until you are satisfied.

Note 1: you will get a better correlation-coefficient r if you reduce the correlation window. Don't compute if over the entire length of the synthetic but focus on the target.

Note 2: stretching and squeezing of synthetics is controversial. You are changing the velocity model at the well location and the question is how much change is reasonable. If your sonic log has already been calibrated by check-shots, there is not much leeway for further modifications. If the logs are bad e.g. due to washouts, you have more freedom.

Best regards,

Paul.

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Paul de Groot

Geoscience Manager

-----------------------------------------------------------------------------------------------------------------------   dGB Earth Sciences
Phone: +31 53 4315155 E-mail: paul.d...@dgbes.com Internet: dgbes.com

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[Jose Regueiro]

STEP 1.....  Check the quality of your data... both seismic and well data.

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José (PEPE) Regueiro, Ph.D

Presidente 

[John Chamberlain]

Step 2 - check the location of your data - both seismic and well!

Regards
John Chamberlain

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[arnab pal]

Thank you so much sir for the response. The higher correlation coefficient r the better it is, but how much r value will be in acceptable limit ?

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From: Paul de Groot <paul.d...@dgbes.com>
Sent: Friday, August 13, 2021 2:39:48 PM
To: OpendTect Users <us...@opendtect.org>
Subject: Re: [OpendTect_Users] Well seismic tie issue

 

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[Roberto Henry Herrera]

Paul,

I wonder if there are plans to include automatic approaches for well to seismic tying.

We did some work about this, with Mirko and Sergey, and it is not hard to implement.

See below:

1- Automatic approaches for seismic to well tying: https://library.seg.org/doi/abs/10.1190/INT-2013-0130.1 

2- A semiautomatic method to tie well logs to seismic data: https://library.seg.org/doi/10.1190/geo2013-0248.1

Since then, I have reviewed variations of these methods and new approaches have been already published in Geophysics. There are good alternatives to explore out there.

Best Regards,

Henry

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[Paul de Groot]

Hi Roberto,

Thanks for suggesting this improvement. 

A refurbishment of the user interface of the well-tie module is in the plans. This is part of an ongoing development project in which we are replacing all log plots in OpendTect. This would be the ideal moment to add semi-automated matching techniques, as well as Roy White's wavelet estimation method. Unfortunately, we don't have a budget to work on such improvements. 

Potential sponsors, or (open source) developers, to take this up are herewith invited to contact me.

Best regards,

Paul.

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Paul de Groot

Geoscience Manager

-----------------------------------------------------------------------------------------------------------------------   dGB Earth Sciences
Phone: +31 53 4315155 E-mail: paul.d...@dgbes.com Internet: dgbes.com

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